#include <iostream>
#include <string>
#include <cctype>

bool vis[30];
std::string s;
int n;

int main()
{
	std::cin >> n >> s;
	for (auto i : s)
		vis[std::toupper(i) - 'A'] = true;
	bool all = true;
	for (int i = 0; i < 26; i++)
		if (!vis[i]) { all = false; break; }
	if (all) std::cout << "YES\n";
	else std::cout << "NO\n";
}

